Photography, whether by the professional or amateur, is an art form wherein the photographer imparts his skills in selecting the subject, lighting, exposure, and choice of film. For example, the photographer may want a high speed black & white film for one subject but a slow, fine grain color film for another, or a color slide film and later a color-negative film, or more commonly a slow speed film to use under bright lighting conditions such as found outdoors and a high speed color-negative film for lower lighting conditions such as found indoors. It has therefore been necessary for the photographer to either carry two or more cameras each loaded with the appropriate film type or to use one camera loaded with different film types which requires unloading one film and replacing it with another. This is a time consuming process that at best delays the time of exposure by a few minutes or at worst causes a complete loss of the photo opportunity. Attempts have been made in the past to build cameras that accepted more than one roll or cassette of film. For example, U.S. Pat. Nos. 2,439,112; 2,616,342; 2,672,796; 3,034,412; 3,805,277 and 5,357,301 all describe cameras with a single objective lens but two pressure plates, supply spools, and take-up spools. Various methods, some rather complex, are described for changing exposure from one film supply to the other, such as by mechanical or optical means. U.S. Pat. No. 2,507,926 describes a camera with a single objective lens capable of exposing multiple films from multiple pressure plates, supply spools, and take-up spools.
Cameras currently being manufactured hold only one film cassette with a fixed number of exposures. In a new line of Advanced Photo System (APS) cameras the more expensive cameras have a feature called mid-roll interrupt. This feature allows the user to remove a film cassette prior to exposing all frames. When this same cassette is reinserted into the camera at a later time, the film is automatically thrust from the cassette and advanced into the film gate to expose the next unexposed frame. This operation requires that the camera have a magnetic read/write head. The APS film has a thin layer of a magnetic recording medium coated on the film base to which the magnetic head can read and write the necessary information that enables mid-roll interrupt. As the lighting conditions change or the photographer moves between indoor and outdoor photography, there is a need to take pictures with film having an ISO speed optimally matched to the changing lighting conditions. In order to expose film with an ISO speed different from that of the film in the camera, it is first necessary to rewind and remove the cassette presently in the camera and then load the camera with a cassette of different film speed. It is therefore necessary for the photographer to have available a second film cassette of the appropriate film speed at the moment when it is the preferred film to use. Most likely this second film cassette will not be available because people do not plan ahead and do not like to carry film in a pocket, purse, or camera bag. If the second cassette is not available at the required moment then the photo opportunity is either lost or the exposure is made with film of the incorrect speed, thereby producing a photographic print of non-optimal image quality. Even when another film cassette is available for this exchange, the amount of time required to perform the exchange is minutes rather than seconds by which time the photo-opportunity may be lost. Prints of non-optimal image quality are typically either grainy, too light or too dark, or lack proper contrast. The lower-cost cameras do not offer the mid-roll interrupt feature. After loading film into the lower-cost cameras, the cassette chamber door is locked and cannot be opened until all frames are exposed or the user elects to remove the film prior to exposing all frames, in which case the remaining frames can never be exposed. There is a need therefore for an improved photographic camera capable of handling multiple cassettes.